Blue Diamonds: Yes, They’re Real – And Expensive

The first thought you may have when you see a glittering blue stone on a woman’s hand is that her sapphire ring is exquisite. Your second thought, when you look a little more closely and see that the gem really resembles a diamond, is that the light is catching the stone in a very unusual way.

There’s another possibility, though: the woman may actually be wearing a rare blue diamond ring.

You’ve probably heard of the Hope Diamond, often called the most famous diamond in existence. What you may not have known is that the Hope Diamond isn’t just famous for being enormous (more than 45 carats) and allegedly cursed – it’s also famous because it’s a beautiful and unusual shade of dark blue. Yes, blue diamonds are most definitely real.

These amazing gemstones have been around for millions of years, of course, because that’s how long it takes for nature to create diamonds of any color. But because of the stones’ extreme rarity and high price, you almost never see blue diamond engagement rings worn in public. And that’s a shame; blue diamond rings are one of the most stunning pieces in the jewelry world.

It’s also a shame that most people don’t know more about these precious, valuable stones and the sheer beauty of the blue diamond rings crafted with them. Here’s our attempt to right that wrong. (We’ll also take a detailed look at treated blue diamonds, which are a very different type of stone.)

Blue Diamonds

Blue diamonds were formed in the earth’s mantle in the same way that all other diamonds were created. Extreme pressure and heat transformed carbon-containing minerals over a period of time that may have lasted billions of years, and the rocks were then “shot” by volcanic eruptions toward the earth’s surface where they cooled and became natural diamonds.

Colored diamonds are created when there are tiny impurities in the stone during the gem’s formation; the blue color of these rare stones is due to trace amounts of the element boron, trapped inside the latticework of the diamond’s crystal structure. The boron absorbs yellow, red and orange light, giving the diamond its unusual blue hue. Interestingly, boron also gives diamonds a strong ability to conduct electricity, which is why natural blue diamond is the hardest material on earth that’s useful as a heat and electrical conductor.

The amount of boron contained in a blue diamond determines the intensity of its color. You can find stones with the deep blue color of a midnight sky, or with the lighter tint of sea water; colors will often be described with terms like “sky blue”, “steel blue”, “baby blue” or “deep blue”. The intensity and color of a blue diamond has a major impact on its value. Some blue diamonds also have secondary undertones which can range from violet to grey, giving them unusual colors or reflective properties. Those with undertones have nitrogen atoms clustered inside the stone and are called type 1a, while purer and more preferable type 2b blue diamonds have little or no nitrogen atoms inside. Most natural blue diamonds are type 2b.

We’ve already mentioned that blue diamonds are extremely rare. How rare are they? Well, start with the fact that (according to many reputable estimates) only 0.01% of all diamonds mined are fancy colored diamonds. Then consider that fewer than 0.1% of those colored diamonds are type 2b blue diamonds, and you can understand why you almost never see a natural blue diamond in the real world. Another way to look at it, courtesy of the Natural Color Diamond Association, is that for every 100 paintings by Picasso that are available at auction, there is just one natural blue diamond. Even so, it’s not the rarest of colored diamonds; red, purple and violet diamonds are even harder to find.

As you’d expect from the rarity of blue diamonds, there are only a few sources of these stones throughout the world. Most come from the Cullinan Mine in South Africa and the Argyle Mine in Australia; a smaller number have been discovered in India, Lesotho and Zimbabwe. Zimbabwe blue diamonds are particularly interesting because they’re the only ones to have been discovered with fluorescent properties. The largest and most valuable blues found in recent years have all come from the Cullinan Mine, including the biggest ever (122 carats) and an incredible vivid blue 30 carat rough stone which was sold for 25 million dollars. Outstanding blue diamonds can come from other sources, though; the Hope Diamond, which we mentioned earlier, was believed to have been discovered in India in the 17th century before it was taken to France for cutting, by the order of King Louis XIV.

Value and Availability of Blue Diamonds

You would expect that the stunning beauty and limited availability of blue diamonds would make them among the priciest gemstones in the world – and you would be correct. Despite the rarity of these gems, demand continues to increase, putting even more upward pressure on prices. Market surveys show that the per-carat cost of natural blue diamonds has grown by double-digits every year over the last decade, even for stones which aren’t the most sought-after dark blue with strong color saturation; prices for light blue diamonds are increasing at the same general rate.

The major reason for this is quite simple: supply and demand. Only a few high-quality large blue diamonds (from which smaller stones are cut) are available at auction each year, where large stones with vivid color regularly sell for one million dollars per carat or more. Some of those gems are sold to collectors and speculators betting on future price increases, driving blue diamond costs even higher while limiting retail availability of the stones.

Prices vary widely at the retail level but it’s not unusual to pay a jeweler more than $10,000 for a high-quality blue diamond that’s smaller than ¼ of a carat, while a half-carat blue stone with intense color can easily cost more than $100,000 (if you can even find one, of course). And if you’re one of the well-to-do shoppers in the market for an eye-popping ring, here’s one benchmark: a six-carat vivid blue diamond ring recently sold for a little over $10 million. You can find natural blue diamond rings for a whole lot less, of course, but be prepared to make major concessions in the areas of color, clarity and cut. Otherwise, prepare to settle for either treated blue diamonds (which are much more affordable but aren’t naturally blue stones) or ones created in a lab (which look gorgeous but obviously aren’t the real thing).

Treated and Lab-Created Blue Diamonds

Treating gemstones with heat, radiation or chemicals to enhance their color or other properties is commonly done. For some gems, such as tanzanite, the treatment is simply cosmetic and has no effect on a stone’s value. However, the process is often used when honest companies are trying to create “products” to meet demand for rare stones like blue diamonds (in which case they’ll divulge the fact that a stone has been enhanced) – or when dishonest companies are trying to deceive buyers into paying top-dollar for a lower-quality gem. Most of the blue diamond engagement rings and blue diamond wedding rings sold at retail actually showcase “normal” white or yellow diamonds which have been heat-treated or irradiated to bring out a blue color, most often using a method called “high pressure high temperature” or HPHT.

It’s important to understand that this enhancement process is very different from the lab creation of materials which are simulated diamonds. When you purchase an enhanced blue diamond ring, it’s still a real diamond with its worth dependent on the “4 C’s”. It’s just not an extremely rare and astronomically-priced natural blue diamond. Expert appraisers and gemologists can tell the difference, which is why it’s even more important than usual to have a full evaluation of the stone in your blue diamond engagement ring performed by a reputable laboratory like GIA, AGS, IGI or EGL.

The lab-created diamonds we’ve just mentioned are another option. Many people feel that because of advancements in laboratory techniques, these “fake” stones look more real and impressive than treated blue diamonds. Believe it or not, though, they’re quite difficult to grow so their cost is quite high, at the same general price level as treated gems. You can expect to pay a few thousand dollars for either a treated or lab-created ½ carat blue diamond, and close to $10,000 for a one-carat treated or grown stone – with exact prices greatly dependent on the “4 C’s”, of course.

Blue and White Diamond Sterling Silver Ring / Ice.com

Selecting A Blue Diamond

If you’ve recently hit the lottery – or your last name is Buffett, Trump or Cruise – a natural blue diamond engagement ring is a trinket which will make an impression at your next family gathering or red carpet entrance. But you can still count on wowing the crowds with a treated or synthetic blue diamond engagement ring, because of those stones’ beauty and relative rarity.

When selecting a blue diamond, you should follow the same evaluation process as you would for any colored diamond, focusing not only on the stone’s cut, clarity, color and carats, but paying particular attention to the hue, tone and saturation of the color. We’ve talked about the ways that people describe the many shades of blue seen in blue diamonds, but when experts grade these gems they use nine levels to rate color: faint, very light, light, fancy light, blue, fancy blue, fancy intense, fancy dark, fancy deep and fancy vivid. The closer you get to “fancy vivid blue” the more valuable the diamond will be, assuming equal grades for the stones’ other attributes. The color saturation (intensity), hue (overall body color) and tone (darkness relative to the hue) will be evaluated as part of this process, as will any secondary colors affecting the hue – and therefore the value – of the gemstone. Secondary colors are added to the description of the diamond, so you might see a stone with a description of “fancy light grayish blue”. If you’re wondering how this corresponds to the D-to-Z diamond color scale you’re familiar with, stones graded “faint” through “light” are roughly equivalent to those normally graded K-to-Z, while the higher-quality gems fall in the D-to-J range. Looking at very light or faint stones can often yield more reasonably-priced “bargains” while still letting you own a blue diamond engagement ring.

The cut of a blue diamond should be in the excellent to good range, but there’s a little extra room to maneuver when it comes to clarity. That’s because the blue color of the stone can obscure minor inclusions. You can safely get away with an I1 stone, as long as the diamond looks eye clean. As far as carats – make sure you bring your American Express Black Card.

Enhanced blue diamonds, since they’re still real diamonds, are evaluated in the same way as their natural blue cousins: clarity, carats, cut and color; getting a full grading of the gemstone by a reputable lab is highly recommended. However, the appearance of an intense blue treated stone’s color, for example, is more a matter of aesthetics than a characteristic which can be rigorously assigned a realistic grade. Also remember that many enhanced blue diamonds look very different than natural ones, so that should be taken consideration when deciding if blue diamond wedding rings or engagement rings are really worth the large investment.

It may surprise you to learn that GIA also grades synthetic diamonds, issuing a report which includes all of the usual measurements, along with grades for synthetic color, synthetic clarity and synthetic cut. Since lab-grown blue diamonds can cost as much as natural clear ones, it makes sense to obtain a full report before spending a fortune on a blue diamond engagement ring – even if it features a synthetic stone.

As you’ve certainly gathered by now, most people can’t realistically afford blue diamond engagement rings, or even blue diamond wedding rings with smaller, less-costly stones. If your heart is set on a ring with a blue gem, you might be better off looking at blue topaz, aquamarine or even sapphire rings. But if you have the cash – and the stomach to spend it on jewelry – few pieces will stand out more than a blue diamond ring.